The design of space-based optical sensors for detection and identification of threat missile launches relies heavily on plume signature simulation models. The development of physics-based plume signature models traces back ~50 years, resulting in very capable models. However, because of the enormous breadth and complexity of the physics and ever-increasing requirements for improved accuracy, higher spatial resolution, and broader spectral coverage, there are many areas where existing models do not adequately predict the signatures of real systems. Spectral Sciences, Inc. proposes to address many of the key model deficiencies through development and validation of innovative, advanced physics-based models for integration into the current state-of-the-art plume signature codes, including the FLITES radiation transport (RT) and the SOCRATES-P high-altitude and RPFM low-altitude flow field codes. The advanced plume signatures models include searchlight scattering, solar and earth shine scattering, photon trapping, hard body plume shine reflection, and molecular condensation. Phase I will feature incorporation of a photon trapping model into legacy codes and its validation against field data, and formulation of Phase II implementation approaches for all the advanced models. Phase II will feature development, integration, and validation of the advanced RT modules.